System and method for traversing vertical obstacles

ABSTRACT

Disclosed is a mobile robot adapted to traverse vertical obstacles. The robot comprises a frame and at least one wheel positioned in a front section of the robot, at least one middle wheel positioned in a middle section of the robot, at least one back wheel positioned in a back section of the robot, and at least one further wheel in the front, middle or back of the robot. The robot also comprises at least one motor-driven device for exerting a downward and/or upward force on the middle wheel and at least two motors for driving the wheels and the motor-driven device. Also disclosed is a method of climbing using a mobile robot as disclosed.

RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/EP2016/076254, filed Oct. 31, 2016, the entire contents of which are hereby fully incorporated herein by reference for all purposes. Application PCT/EP2016/076254 claims priority from: (i) European Patent Application No. 15192648.2, filed Nov. 2, 2015; (ii) European Patent Application No. 15198094.3, filed Dec. 4, 2015; and (iii) International Patent Application No. PCT/EP2016/025047, filed May 25, 2016, the entire contents of each of which are hereby fully incorporated herein by reference for all purposes.

FIELD

The invention relates to a mobile robot. More particularly, the invention relates to a mobile robot adapted to traverse generally vertical obstacles such as curbstones and the like.

INTRODUCTION

Motion in outdoor environment can require traversing obstacles. When moving exclusively on car roads, no major obstacles are traversed. However, movement on pedestrian walkways for example can require crossing car roads, which can require traversing vertical obstacles such as curbstones. Vehicles aiming to travel outdoors, in particular on pedestrian walkways, can comprise a device adapted for climbing vertical obstacles. Such a device can be present for example in wheelchairs, in curb sweeping vehicles, or in off-road vehicles.

U.S. Pat. No. 3,649,981 discloses a road sweeper of the three wheel type having forward and rear traveling wheels and adapted for the climbing of curbs or dividers onto raised surfaces by the provision of lifter wheels bodily movable between raised and lowered positions to elevate the vehicle and its traveling wheels for movement onto and off the raised surface.

U.S. Pat. No. 4,817,747 describes an all-terrain vehicle having six wheels with three wheels on each side. Two of the wheels on each side are mounted on one pivotal bogie, and one wheel is mounted on another pivotal bogie, and the bogies are coupled to each other to always assume the same inclination to the horizontal centerline of the vehicle chassis in all pivotal positions thereof All wheels are positively driven by gearing which includes gearing in the bogies.

WO patent application 2005/051279 A1 describes an invention related to an electric wheelchair. The inventive wheelchair comprises a frame which is mounted on two drive shafts that are actuated by electric motors, and two climbing mechanisms that tilt in relation to the said shafts. According to the invention, the climbing mechanism enables the chair to move forward horizontally and to be inclined by tilting the mechanism in relation to the drive shaft, thereby raising or lowering same in order to pass over uneven surfaces.

SUMMARY

The present invention is specified in the claims as well as in the below description. Preferred embodiments are particularly specified in the dependent claims and the description of various embodiments.

The present invention is directed to a mobile robot. The robot can particularly drive autonomously and/or semi-autonomously. It can be adapted to traverse at least generally vertical or vertical obstacles, such as curbstones. It will be understood that also in one, two and/or three dimension(s) inclined obstacles or bumps can be traversed.

A robot according to the present invention can be a machine, device, unit, assembly, system etc. being able to carry out a series of actions automatically and may further be programmable by respective computing hardware and software. One of the actions can be driving, particularly in autonomous and/or semi-autonomous fashion. Semi-autonomous operation of the robot can mean that a third party, such as an operator, can control the robot by providing commands to the robot to direct the robot along a path, for example when traversing vertical obstacles. The operator can further communicate with people in the immediate proximity of the robot through the microphone and speakers that can be mounted on the robot.

The robot can comprise a frame structure or undercarriage having a front end and a back end, and further having a front section, a middle section and a back section. The robot can comprise at least one front wheel positioned in the front section of the robot and extending beyond it in the front. Further, it can comprise at least one back wheel positioned in the back section of the robot, and at least one middle wheel positioned in the middle section of the robot. Moreover, at least one further wheel positioned either near the front, middle and/or back of the structure can be provided, particularly in order to prevent any severe tilting to the side.

The robot can further comprise a motor-driven device for exerting a downward and/or an upward force with respect to the ground, selectively on the at least one middle wheel. The robot can comprise at least two motors, each of which can be adapted to drive the wheels and/or the motor-driven device.

The robot can comprise also more than the at least four wheels as specified before. E.g., it can comprise 6 wheels with a pair of wheels in the front, one pair in the middle and one pair in the rear. However, this is not necessary in order to fulfill the invention, as will be further understood from the following.

The motor-driven device is adapted so that when the robot encounters a vertical obstacle along its direction of movement, a downward and/or upward force can be applied by the motor-driven device through the at least one middle wheel, to facilitate the traversal of the vehicle across the vertical obstacle. In case of a pair of middle wheels or more than that, these wheels can be moved downwardly and/or upwardly. This can be done by any mechanism.

The motor-driven device can be adapted to provide a downward and/or upward force through at least one middle wheel that can be located behind (towards the rear) of the center of mass of the robot.

The motor-driven device can further be adapted to exert a downward and/or upward force through the at least one back wheel. In case the robot is driving over ground or traversing an obstacle, the downward movement of the middle wheel(s) makes the robot tilt around a tilting axis that can be perpendicular to the direction of driving. The front wheel(s) and/or back wheel(s) can further assist this. When the front wheel(s) touch the vertical or inclined surface of the obstacle its/their traction applied to this surface can help the robot to climb the obstacle. Preferably, the middle wheel(s) and/or the rear wheel(s) assist the front wheel(s) to maintain touch with this surface. The middle wheel(s) and their relative movement further assist to allow the front wheel and the robot to climb the obstacle and/or to keep the traction of the front wheel(s) on top and/or behind the obstacle. This will be further described below.

The robot can further comprise a sensing device for sensing obstacles along its forward direction of motion. The sensing device comprises at least one of: ultrasonic sensor, Lidar sensor, optical flow sensor, stereo vision sensor, map-based localization device, bumping sensor, odometry-based sensor and wheel slippage sensor. Also a wheel-based model inter alia taking into consideration the driving but lack of turning of the wheels can be used.

The sensing device can be adapted to trigger the motor-driven device such that a downward force is applied to at least the middle wheels of the robot to facilitate the movement of the front wheels across the obstacles.

The motor-driven device can be further adapted to communicate with the sensing device and apply a downward and/or upward force on at least the middle wheels based on information from the sensing device.

The motor-driven device can be adapted to alternately apply downward force to the middle wheels and the back wheels based on information from the sensing device.

The sensing device can comprise means for communicating with a central processing unit, wherein the central processing unit provides instructions to the motor-driven device based on information received from the sensing device.

At least one tilting lever (tilting shaft) can be provided connecting at least one middle and one back wheel, preferably two shafts connecting middle and back wheels on each of the left and the right sides of the robot.

The tilting lever can be adapted for at least angular motion in the plane of the robot's wheels in order to apply a downward and/or upward force with respect to the ground.

The robot can further comprise at least two middle wheels and two back wheels, wherein the motor-driven device comprises a motor and two tilting levers and wherein one set of wheels comprising at least one middle wheel and a back wheel is connected to a first tilting lever, and a second set of at least one middle wheel and a back wheel is connected to a second shaft, and wherein the first and second tilting levers are connected to a rear axle at a first and second pivot point on the first and second tilting levers, respectively.

The tilting lever can rotate freely and/or be actuated by a motor. The tilting shaft can rotate around a lever bearing (tilting axle) that can be located between the respective axial centers of rotation of each pair of wheels.

Opposing wheels can also be arranged without being connected to each other but to the neighboring wheels by the tilting lever. In this case a lever turning motor can be arranged for each side of the robot, e.g. tilting the middle wheel and the rear wheel on the same side and assisting climbing.

The tilting lever can rotate or be rotated around the lever bearing by at most 60°, preferably on either side, i.e. clockwise and counter clockwise. More preferably, the tilting lever can be turned around the lever bearing by at most 55°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 50°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 45°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 40°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 35°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 30°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 25°, preferably on either side. More preferably, the tilting lever can be turned around the lever bearing by at most 20°, preferably on either side.

Accordingly, the invention also provides a robot comprising a frame with at least one front wheel, at least two middle wheels and at least two rear wheels, wherein at least one middle wheel and at least one rear wheel are connected by a tilting lever that is arranged on each of opposing sides of the frame; and wherein each tilting lever can be turned around a lever bearing located between the respective axial centers of rotation of each pair of wheels. There can be one pair of middle of back wheels that are arranged on one tilting lever that is arranged on one side of the frame, and another pair of middle and back wheels that are arranged on a second tilting lever that is arranged on or to an opposing side of the frame. The tilting levers can be connected to respective lever shafts via a lever bearing.

The tilting levers on each side can rotate freely and/or can be actuated independently by at least one lever turn motor. During free rotation the motor can be in an unactuated state, thereby damping the tilting of the tilting lever by its resistance. Alternatively or additionally a clutch can be arranged, disconnecting the lever turn motor from the respective turning lever so that tilting can take place without any or less resistance, particularly when the robot is moving and the respective middle wheel and connected rear wheel can tilt according to the topography of the ground.

For example, the clutch can be controlled so as to leave the lever turn motor disconnected when not traversing difficult and/or vertical obstacles, and connect the motor when needed to traverse such obstacles.

The tilting lever would be useful for robot balance and for minimizing vibration and reducing wear during the motion of the robot, for example when the robot is moving across an uneven terrain. The tilting levers can also facilitate increased traction, by ensuring that the wheels touch ground when traversing uneven surfaces. Further, when the robot is equipped with cameras for visualization purposes, increased stability is beneficial. The tilting levers on either side of the robot can also move independently, either when the tilting levers move freely around the lever bearing or when the tilting levers are rotated by means of a motor. This way, the configuration of the tilting lever on either side may be different during operation of the robot.

The robot may further comprise at least one sensor adapted to sense the absolute and/or relative angular position of the tilting lever. This sensor can preferably be a Hall Effect non-contact rotary position sensor. The sensor can also be any one or a combination of at least one potentiometer, at least one optical encoder, at least one magnetic encoder and/or at least one visual camera-like system.

The sensor adapted to sense the relative angular position of the tilting lever can be calibrated at the beginning of robot operation, or during setup of the robot, preferably by moving the lever to an extreme position and by calibrating it there. The sensor can be recalibrated whenever deemed desirable, such as daily, more preferably weekly, more preferably monthly. In a preferred embodiment, the calibration process can be automated and performed by the robot itself as part of a diagnostics program.

In another embodiment, the tilting lever can be actuated by a motor. The motor can engage right from the start of desired rotation of the tilting lever or after the tilting angle reaches a certain value. This value can depend on the precise task the robot is accomplishing. The motor can engage after receiving particular sensor data from the sensor adapted to sense the angular position of the tilting lever.

In a preferred embodiment, the robot can be adapted to climb obstacles of up to 5 cm, more preferably up to 8 cm, more preferably up to 10 cm, even more preferably up to 15 cm, even more preferably up to 18 cm, or even more preferably up to 20 cm, with or without engaging a motor driving the tilting lever.

In a preferred embodiment, the tilting lever can be adapted to rotate freely until a certain angle, at which point the tilting turn motor is adapted to engage. The tilting turn motor can be adapted to engage after the tilting lever has rotated freely for at least 10°, more preferably such as at least 15°, more preferably such as at least 20° and even more preferably such as at least 25°.

In a preferred embodiment, the tilting lever can be adapted to rotate freely over a range of 25°-45° from one engagement point to the next. In such an embodiment, the tilting turn motor can be adapted to engage or to start actuating when the tilting lever reaches an engagement point.

In one embodiment, the robot can be adapted to move over uneven ground without engaging the lever turn motor, i.e. simply by rotating the tilting lever freely. Uneven ground can refer to any surface comprising bumps or holes, such as a is walkway comprising cobblestones, low kerbstones or curbstones, ground comprising plants or stones or rocks, concrete with indentations in the surface and other features leading to departures from a smooth surface.

The motor-driven device can be adapted for exerting angular force on the first and second tilting lever about the first and second pivot points, so as to alternately generate a downward force on the middle wheels and the back wheels.

The motor-driven device can be further adapted to lift the middle wheels, so that during climbing, their rotational center transiently extends vertically beyond that of the front wheels', with respect to the vehicle frame or undercarriage.

The motors driving the wheels can be electrical motors. Any kind of electrical motors known in the art for driving purposes can be used.

The front wheels can be driven. More preferably all of the wheels can be driven.

The motor-driven device can comprise at least one piston-driven device adapted to drive at least one wheel in a vertical direction with respect to the ground.

The motor-driven device can comprise two piston-driven devices for driving the middle wheels in a vertical direction with respect to ground.

The robot can comprise at least 4 (four) electric motors adapted to drive the wheels, such as with two motors for driving each of the two front wheels and two motors for driving two sets of middle and back wheels, each of said motors driving at least one middle wheel and a back wheel that is disposed along one side of the robot.

The robot's center of mass can be located between the middle and the front end of the robot. The robot's center of mass can be located between the middle of the robot and half of the distance from the middle to the front end of the robot. The center of mass can also comprise any delivery the robot may transport.

The robot can be adapted for motion in an unstructured outdoor environment. The robot can be adapted to traverse vertical obstacles of a height of about 10 to about 25 cm, such as about 15 to about 20 cm, such as curbstones.

In the present context, a wheel includes tires that are mounted thereon, preferably on the outer rim.

The wheel diameter of a robot can amount to 10-30 cm, preferably 15-25 cm, more preferably about 20 cm. Generally, the invention can be realized using combinations of wheels that are of different diameters. The wheels of the robot are in one embodiment of similar dimensions. The wheels can also be of substantially identical diameter.

The front wheels can protrude in front of the frame structure by 1 to 8 cm, preferably by 1 to 6 cm, more preferably by 2 to 5 cm.

The wheels can protrude beneath the frame by at least 5 cm, preferably at least 6 cm, more preferably by at least 7 cm.

The wheels can comprise pneumatic tires, for example tires made of a natural rubber or caoutchouc compound and/or synthetic rubber. The wheels can also comprise solid tires. Synthetic rubber can be any suitable artificial elastomer, such as those synthesized from petroleum by-products. Examples of synthetic rubber include styrene-butadiene rubbers, which are made from styrene and butadiene. Other synthetic rubbers can be made from isoprene, chloroprene and/or isobutylene monomers, and can also include isoprene for crosslinking The wheels can also comprise silicon tires.

The tires can be essentially smooth, or the tires can be grooved, symmetrically or asymmetrically. The grooves can be of any suitable depth and orientation, as known to the skilled person. The tires can be studded. It can also be convenient to change the type of tire depending on the season or the terrain in which the robot is operating.

The wheels can have a static friction coefficient μ_(s) between the wheels and the obstacle is 0.9-1.1 for dry surface and 0.2-0.4 for wet surface.

The front wheel(s), the back wheel(s) and the canter wheel(s) can be arranged in an undercarriage or frame structure such that the robot is supported by at least two wheels during normal travel along a surface.

The robot can further comprise an enclosed space for holding at least one delivery, preferably comprising a secure access device for providing access to the space. The secure access device comprises a closure mechanism and/or a lid that is controlled by a secure interface.

With a delivery comprised within the robot, the center of mass of the combination can be located between the middle and the front end of the robot.

The robot can be adapted to traverse at least vertical obstacles, the robot comprising a frame structure having a front end and a back end, the robot comprising at least one pair of front wheels positioned in proximity of the front end of the structure, at least one pair of back wheels positioned towards the back end of the structure and at least one pair of middle wheels positioned in between the front and back wheels. Moreover, at least two motors are provided that are adapted to drive the wheels. At least one pushing device for exerting a downward force with respect to the ground, selectively on the at least one middle wheel can be further provided.

A motor, preferably an electrical motor, can drive the pushing device. The pushing device can be adapted such that when the robot encounters a vertical obstacle along its direction of movement, the device actuates at least one pair of middle wheels, to facilitate the traversal of the vehicle across the vertical obstacle, by applying a downward and/or upward force on the middle wheels.

The pushing device can be further adapted to exert a downward and/or upward force through at least one pair of back wheels.

The motor-driven device and/or the pushing device can exert counteracting force on the middle and back wheels, so that when a downward force is applied to the middle wheels, a counteracting upward force is simultaneously applied to the back wheels, and when an upward force is applied to the middle wheels, a counteracting downward force is simultaneously applied to the back wheels. The force that is applied to the wheels by the pushing device can be equal in magnitude.

The robot can comprise a sensing device for sensing obstacles along its forward direction of motion.

The sensing device can be adapted to trigger the pushing device such that a downward force is applied to at least the pair of middle wheels of the robot to facilitate the movement of the front wheels over the obstacles.

The sensing device can comprise at least one of: ultrasonic sensor, Lidar sensor, optical flow sensor, stereo vision sensor, map-based localization device, bumping sensor, odometry-based sensor and wheel slippage sensor.

The pushing device can be further adapted to communicate with the sensing device and apply a downward and/or upward force on the middle wheels based on information or instructions from the sensing device.

The pushing device can comprise at least one tilting lever connecting at least one middle and one back wheel, preferably two shafts connecting middle and back wheels on each of the left and the right sides of the robot.

The pushing device can be adapted to alternately apply force to the middle wheels and the back wheels based on information from the sensing device.

The sensing device can comprise means for communicating with a central processing unit, and wherein the central processing unit provides instructions to the pushing device based on information received from the sensing device.

The tilting lever can be adapted for at least angular motion in the plane of the robot's wheels in order to apply a downward and/or upward force with respect to the ground.

The pushing device can comprise a motor, and wherein the first and second tilting levers are connected to a rear axle at a first and second pivot point on the first and second axles, respectively.

The pushing device can be adapted for exerting angular force on first and second shafts about the first and second pivot points, so as to alternately generate a downward force on the middle wheels and the back wheels.

The middle and/or back wheels can, during climbing transiently be displaced towards or away from the body of the robot. Consider for example the robot starting to climb an obstacle. The front wheels start climbing up the obstacle, which means that the body of the robot is now tilted with respect to the ground on which the middle and back wheels rest. As a consequence of the middle and back wheels being connected on tilting levers that are mounted on an axis, the middle wheel will move away from the body, while the back wheel will move towards the body. As the middle wheels start to move up the obstacle, the relative position of the middle and back wheels with respect to the body will be reversed, i.e. the middle wheels will move towards the body, and the back wheels away from the body. Accordingly, the pushing device can be adapted to lift the middle wheels, so that during climbing, their rotational center can transiently extend vertically beyond that of the front wheels, with respect to the vehicle frame. For example, if the wheels are of similar or identical diameter, the center of the middle wheels will extend vertically beyond that of the front wheels, to maintain contact with the obstacle being climbed during the climbing. At the same time, the rear wheels can be moved away from the body which further supports the moving of the robot's front upwardly.

A mobile robot can be further adapted to traverse vertical obstacles with a predefined height. The robot can comprise a frame structure having a front end and a back end, the robot comprising at least one pair of front wheels positioned in proximity of the front end of the structure, at least one pair of back wheels positioned towards the back end of the structure and at least one pair of middle wheels positioned in between the front and back wheels. In one embodiment, the wheels of the robot have radius r. The maximum allowable distance between the front and middle wheels can be described by the equation

${d = \frac{{6\; r^{2}} - {3\; {h \cdot r}}}{2\left( {h - r} \right)}},$

where d is the said maximum distance, r is the radius of the wheel and h is the predefined height of the vertical obstacle. Accordingly, in one embodiment, the wheels of the robot have a radius r and the robot can further be characterized by a maximum distance d between the at least one front wheel and the at least one middle wheel measured from the rear-most facing point of the at least one front wheel to the front-most facing point of the at least one middle wheel of

${d = \frac{{6\; r^{2}} - {3\; {h \cdot r}}}{2\left( {h - r} \right)}},$

where d is the said maximum distance, r is the radius of the wheel and h is the predefined height of the vertical obstacle.

The frame structure can comprise an undercarriage that is structured so as to be in vertical proximity of a line connecting the rear-most facing point of the at least one front wheel to the front-most facing point of the at least one middle wheel.

The middle and back wheels can also have a maximum distance d between the at least one middle wheel and the at least one back wheel measured from the rear-most facing point of the at least one middle wheel to the front-most facing point of the at least one back wheel defined by

$d = \frac{{6\; r^{2}} - {3\; {h \cdot r}}}{2\left( {h - r} \right)}$

where d is the said maximum distance, r is the radius of the wheel and h is the height of the vertical obstacle to be traversed.

The frame structure can also comprise an undercarriage that is structured so as to be in vertical proximity of the line connecting the rear-most facing point of the at least one middle wheel to the front-most facing point of the at least one back wheel.

The robot can be adapted to traverse vertical obstacles of at least 18 cm height with wheel radius of at least 10 cm and the maximum distance between the front and middle wheels and/or the middle and back wheels measured from the rear-most facing point of the front wheel and/or middle wheel respectively to the front-most facing point of the middle and/or back wheel of 4 cm.

The robot can further comprise a sensing device for sensing obstacles along its forward direction of motion.

The sensing device can be adapted to trigger the pushing device such that a downward force is applied to at least the pair of middle wheels of the robot to facilitate the movement of the front wheels over the obstacles.

The sensing device can comprise means for communicating with a central processing unit, wherein the central processing unit provides instructions to the pushing device based on information received from the sensing device.

The tilting lever can be adapted for at least angular motion in the plane of the robot's wheels in order to apply a downward and/or upward force with respect to the ground.

The pushing device can comprise a motor, and wherein the first and second tilting levers are connected to a rear axle at a first and second pivot point on the first and second axles, respectively.

The pushing device can be adapted for exerting angular force on first and second shafts about the first and second pivot points, so as to alternately generate a downward force on the middle wheels and the back wheels.

The pushing device can be adapted to lift the middle wheels, so that during climbing, their rotational center can transiently extend vertically beyond that of the front wheels', with respect to the vehicle frame.

The invention is also directed to a method comprising the steps of approaching a vertical obstacle with a mobile robot comprising a frame structure having a front end and a back end, the robot comprising at least one front wheel positioned in proximity of the front end of the structure, at least one back wheel positioned in proximity of the back end of the structure, and at least one middle wheel positioned in between the front and back wheels, and at least one further wheel either in a front, middle and/or back position; wherein the at least one front wheel, the at least one back wheel and the at least one middle wheel are arranged on the frame structure such that the robot is supported by said wheels during normal travel along a surface; the robot further comprising at least two motors adapted to drive the wheels, and a motor-driven device for exerting a downward force with respect to the ground, selectively on at least the at least one middle wheel;

sensing the vertical obstacle with one or more sensing devices disposed on the robot;

actuating the one or more front wheels with one or more motors to permit the one or more front wheels to start climbing the vertical obstacle;

actuating the one or more middle and/or back wheels with one or more motors to provide a forward momentum of the robot and thereby increase friction between the one or more front wheels and the vertical obstacle;

exerting a downward force on the one or more middle wheels with the motor-driven device so as to provide a counteracting vertical force on the one or more front wheels and increase traction of the middle wheels, thereby facilitating the climbing of the front wheels;

cease applying the downward force on the one or more middle wheels after the front wheels have reached the top of the obstacle; and

complete climbing of the obstacle through the forward momentum of the robot generated by actuating the middle and/or back wheels.

The actuation of front, middle and/or back wheels can be performed simultaneously. The force applied by the wheels leads to increased traction of the front wheels on the curbstone, aiding in the climbing of the front wheels.

The front, middle and back wheels can all be actuated as the robot approaches the vertical obstacle.

The method can further comprise sensing the position of the front wheels on the obstacle by means of the at least one sensing device before ceasing applying the downward force on the one or more middle wheels.

The motor-driven device can comprise a mechanism for providing alternating downward and upward force on the middle wheels and back wheels, and wherein the method further comprises in the previously mentioned step of ceasing applying the downward force exerting an upward force on the back wheels simultaneously to the exerting a downward force on the middle wheels, by means of the motor-driven device, and wherein the method further comprises

reversing the application of force on the middle and back wheels, so that a downward force is applied to the back wheels and an upward force on the middle wheels, to facilitate the climbing of the middle wheels of the obstacle, and

completing climbing of the obstacle through the forward momentum of the robot generated by actuating the middle and/or back wheels.

The method can further comprise ceasing applying downward or upward force on the middle or back wheels after the sensing device determines that the back wheels have reached the top of the obstacle.

A skilled reader will understand, that any method described above or below and/or claimed and described as a sequence of steps is not restrictive in the sense of the order of steps.

Below, further numbered embodiments of the invention will be discussed.

-   -   1. A mobile robot adapted to traverse at least vertical         obstacles, the robot comprising a frame structure having a front         end and a back end, and further having a front section, a middle         section and a back section, the robot comprising         -   (a) at least one front wheel positioned in the front section             of the robot and extending beyond it in the front, at least             one back wheel positioned in the back section of the robot,             and at least one middle wheel positioned in the middle             section of the robot;         -   (b) at least one further wheel positioned either in the             front section, middle section and/or back section of the             structure;     -   and wherein the robot further comprises         -   (c) a motor-driven device for exerting a downward and/or             upward force with respect to the ground, selectively on the             at least one middle wheel; and         -   (d) at least two motors, each of which being adapted to             drive the wheels and/or the motor-driven device.     -   2. A robot according to the previous embodiment, wherein the         motor-driven device is adapted such that when the robot         encounters a vertical obstacle along its direction of movement,         a downward and/or upward force can be applied by the         motor-driven device through the at least one middle wheel, to         facilitate the traversal of the vehicle across the vertical         obstacle.     -   3. A robot according to any of the preceding embodiments,         wherein the motor-driven device is further adapted to exert a         downward and/or upward force through the at least one back         wheel.     -   4. A robot according to any of the preceding embodiments,         wherein the robot further comprises a sensing device for sensing         obstacles along its forward direction of motion.     -   5. A robot according to the previous embodiment, wherein the         sensing device comprises at least one of: ultrasonic sensor,         Lidar sensor, optical flow sensor, stereo vision sensor,         map-based localization device, bumping sensor, odometry-based         sensor and wheel slippage sensor.     -   6. A robot according to the previous two embodiments, wherein         the sensing device is adapted to trigger the motor-driven device         such that a downward force is applied to at least the middle         wheels of the robot to facilitate the movement of the front         wheels across the obstacles.     -   7. A robot according to any one of the previous three         embodiments, wherein the motor-driven device is further adapted         to communicate with the sensing device and apply a downward         and/or upward force on at least the middle wheels based on         information from the sensing device.     -   8. The robot according to the previous embodiment, wherein the         motor driven device is adapted to alternately apply downward         force to the middle wheels and the back wheels based on         information from the sensing device.     -   9. A robot according to the previous embodiment, wherein the         sensing device comprises means for communicating with a central         processing unit, and wherein the central processing unit         provides instructions to the motor-driven device based on         information received from the sensing device.     -   10. A robot according to any one of the preceding embodiments         further comprising at least one tilting lever connecting at         least one middle and one back wheel, preferably two shafts         connecting middle and back wheels on each of the left and the         right sides of the robot.     -   11. A robot according to the preceding embodiment wherein the         tilting lever is adapted for at least angular motion in the         plane of the robot's wheels in order to apply a downward and/or         upward force with respect to the ground.     -   12. A robot according to any of the preceding embodiments,         wherein the robot comprises at least two middle wheels and two         back wheels, wherein the motor-driven device comprises a motor         and two tilting levers and wherein one set of wheels comprising         at least one middle wheel and a back wheel is connected to a         first tilting lever, and a second set of at least one middle         wheel and a back wheel is connected to a second tilting lever,         and wherein the first and second tilting levers are connected to         a rear axle at a first and second pivot point on the first and         second tilting levers, respectively.     -   13. A robot according to the preceding embodiment, wherein the         motor-driven device is adapted for exerting angular force on the         first and second tilting lever about the first and second pivot         points, so as to alternately generate a downward force on the         middle wheels and the back wheels.     -   14. A robot according to any of the preceding embodiments         wherein the motor-driven device is further adapted to lift the         middle wheels, so that during climbing, their rotational center         transiently extends vertically beyond that of the front wheels',         with respect to the vehicle frame.     -   15. A robot according to any of the preceding embodiments         wherein the motor-driven device is further adapted to lift         and/or push down the back wheels, so that when a downward force         is applied to the middle wheels, a counteracting upward force is         simultaneously applied to the back wheels, and when an upward         force is applied to the middle wheels, a counteracting downward         force is simultaneously applied to the back wheels.     -   16. A robot according to any of the preceding embodiments         wherein the motors driving the wheels are electrical motors.     -   17. A robot according to any of the preceding embodiments         wherein the front wheels are driven.     -   18. A robot according to any of the preceding embodiments         wherein all of the wheels are driven.     -   19. A robot according to any of the preceding embodiments         wherein the motor-driven device comprises at least one         piston-driven device adapted to drive at least one wheel in a         vertical direction with respect to the ground.     -   20. The robot according to the previous embodiment, wherein the         motor-driven device comprises two piston-driven devices for         driving the middle wheels in a vertical direction with respect         to ground.     -   21. A robot according to any of the preceding embodiments         comprising at least 4 (four) electric motors adapted to drive         the wheels.     -   22. The robot according to the previous embodiment, comprising         two motors for driving each of two front wheels and two motors         for driving two sets of middle and back wheels, each of said         motors driving at least one middle wheel and a back wheel that         is disposed along one side of the robot.     -   23. A robot according to any of the preceding embodiments         wherein the robot's center of mass is located between the middle         and the front end of the robot.     -   24. A robot according to any of the preceding embodiments         wherein the robot's center of mass is located between the middle         of the robot and half of the distance from the middle to the         front end of the robot.     -   25. A robot according to any of the preceding embodiments         adapted for motion in an unstructured outdoor environment.     -   26. A robot according to any of the preceding embodiments         adapted to traverse vertical obstacles of a height of about 10         to about 25 cm, such as about 15 to about 20 cm, such as         curbstones.     -   27. A robot according to any of the preceding embodiments         wherein the wheel diameter is 10-30 cm, preferably 15-25 cm,         more preferably about 20 cm.     -   28. A robot according to any of the preceding embodiments,         wherein the front wheels protrude in front of the frame         structure by 1 to 8 cm, preferably by 1 to 6 cm, more preferably         by 2 to 5 cm.     -   29. A robot according to any of the preceding embodiments         wherein the wheels protrude beneath the frame by at least 5 cm,         preferably at least 6 cm, more preferably by at least 7 cm.     -   30. A robot according to any of the preceding embodiments         wherein the wheels comprise pneumatic tires made of a caoutchouc         compound and/or synthetic rubber.     -   31. A robot according to any of the preceding embodiments         wherein the static friction coefficient μ_(s) between the wheels         and the obstacle is 0.9-1.1 for dry surface and 0.2-0.4 for wet         surface.     -   32. A robot according to any of the preceding embodiments         wherein the front wheel(s), the back wheel(s) and the center         wheel(s) are arranged on the frame structure such that the robot         is supported by at least two wheels during normal travel along a         surface.     -   33. The robot according to any one of the preceding embodiments,         further comprising an enclosed space for holding at least one         delivery.     -   34. The robot according to the preceding embodiment, further         comprising a secure access device for providing access to the         space.     -   35. The robot according to the preceding embodiment, wherein the         secure access device comprises a closure mechanism that is         controlled by a secure interface.     -   36. A combination of a robot according to any of the preceding         embodiments and a delivery comprised within the robot, wherein         the center of mass of the combination is located between the         middle and the front end of the robot.     -   37. A mobile robot adapted to traverse at least vertical         obstacles, the robot comprising a frame structure having a front         end and a back end, the robot comprising         -   (a) at least one pair of front wheels positioned in             proximity of the front end of the structure, at least one             pair of back wheels positioned towards the back end of the             structure and at least one pair of middle wheels positioned             in between the front and back wheels;         -   (b) at least two motors adapted to drive the wheels; and         -   (c) at least one pushing device for exerting a downward             force with respect to the ground, selectively on the at             least one middle wheel.     -   38. A robot according to embodiment 37 wherein the pushing         device is driven by a motor, preferably an electrical motor.     -   39. A robot according to any of the preceding two embodiments,         wherein the pushing device is adapted such that when the robot         encounters a vertical obstacle along its direction of movement,         a downward and/or upward force can be applied by the device         through at least one pair of middle wheels, to facilitate the         traversal of the vehicle across the vertical obstacle.     -   40. A robot according to any of the preceding three embodiments,         wherein the pushing device is further adapted to exert a         downward and/or upward force through at least one pair of back         wheels.     -   41. A robot according to any of the embodiments 37 to 40,         wherein the robot further comprises a sensing device for sensing         obstacles along its forward direction of motion.     -   42. A robot according to the previous embodiment, wherein the         sensing device is adapted to trigger the pushing device such         that a downward force is applied to at least the pair of middle         wheels of the robot to facilitate the movement of the front         wheels over the obstacles.     -   43. A robot according to any one of the previous two         embodiments, wherein the sensing device comprises at least one         of: ultrasonic sensor, Lidar sensor, optical flow sensor, stereo         vision sensor, map-based localization device, bumping sensor,         odometry-based sensor and wheel slippage sensor.     -   44. A robot according to any one of the previous three         embodiments, wherein the pushing device is further adapted to         communicate with the sensing device and apply a downward and/or         upward force on the middle wheels based on information from the         sensing device.     -   45. A robot according to any one of the embodiments 37 to 44,         wherein the pushing device comprises at least one tilting lever         connecting at least one middle and one back wheel, preferably         two shafts connecting middle and back wheels on each of the left         and the right sides of the robot.     -   46. The robot according to the previous embodiment, wherein the         pushing device is adapted to alternately apply force to the         middle wheels and the back wheels based on information from the         sensing device.     -   47. A robot according to the previous embodiment, wherein the         sensing device comprises means for communicating with a central         processing unit, and wherein the central processing unit         provides instructions to the pushing device based on information         received from the sensing device.     -   48. A robot according to any of the preceding three embodiments         wherein the tilting lever is adapted for at least angular motion         in the plane of the robot's wheels in order to apply a downward         and/or upward force with respect to the ground.     -   49. A robot according to any of the preceding embodiments 46 to         48, wherein the pushing device comprises a motor, and wherein         the first and second tilting levers are connected to a rear axle         at a first and second pivot point on the first and second axles,         respectively.     -   50. A robot according to the preceding embodiment, wherein the         pushing device is adapted for exerting angular force on first         and second shafts about the first and second pivot points, so as         to alternately generate a downward force on the middle wheels         and the back wheels.     -   51. A robot according to any of the preceding embodiments 37 to         50, wherein the pushing device is adapted to lift the middle         wheels, so that during climbing, their rotational center can         transiently extend vertically beyond that of the front wheels',         with respect to the vehicle frame.     -   52. A robot according to any of the preceding embodiments 37 to         51, wherein the pushing device is further adapted to lift and/or         push down the back wheels, so that when a downward force is         applied to the middle wheels, a counteracting upward force is         simultaneously applied to the back wheels, and when an upward         force is applied to the middle wheels, a counteracting downward         force is simultaneously applied to the back wheels.     -   53. A robot according to any of the preceding embodiments 37 to         52 wherein the motors driving the wheels and/or the pushing         device are electrical.     -   54. A robot according to any of the preceding embodiments 37 to         53, wherein the front wheels are driven.     -   55. A robot according to any of the preceding embodiments 37 to         54 comprising at least 4 (four) electric motors adapted to drive         the wheels.     -   56. A robot according to any of the preceding embodiments 37 to         55, wherein the robot's center of mass is located between the         middle and the front end of the robot.     -   57. A robot according to any of the preceding embodiments 37 to         56, wherein the robot's center of mass is located between the         middle of the robot and half of the distance from the middle to         the front end of the robot.     -   58. A robot according to any of the preceding embodiments 37 to         57, adapted for motion in an unstructured outdoor environment.     -   59. A robot according to any of the preceding embodiments 37 to         58, adapted to traverse vertical obstacles of a height of 10-30         cm, preferably 15-25 cm, more preferably about 20 cm.     -   60. A robot according to any one of the preceding embodiments 37         to 59, wherein the pairs of front, middle and back wheels are         connected on respective axles.     -   61. The robot according to the previous embodiment, wherein the         distance between wheels on each of the axles is approximately         equal.     -   62. A robot according to any of the preceding embodiments 37 to         61, wherein the wheel diameter is 10-30 cm, preferably 15-25 cm,         more preferably about 20 cm.     -   63. A robot according to any of the preceding embodiments 37 to         62, wherein the wheels protrude beneath the frame by at least 5         cm, preferably at least 6 cm, more preferably by at least 7 cm.     -   64. A robot according to any of the preceding embodiments 37 to         63, wherein the front wheels protrude in front of the frame         structure by 1 to 8 cm, preferably by 1 to 6 cm, more preferably         by 2 to 5 cm.     -   65. A robot according to any of the preceding embodiments 37 to         64, wherein the wheels comprise pneumatic tires made of a         caoutchouc compound and/or synthetic rubber.     -   66. A robot according to any of the preceding embodiments 37 to         65, wherein the static friction coefficient μ_(s) between the         wheels and the obstacle is 0.9-1.1 for dry surface and 0.2-0.4         for wet surface.     -   67. The robot according to any one of the preceding embodiments         37 to 66, further comprising a space for holding at least one         delivery.     -   68. The robot according to any one of the preceding embodiments         37 to 67, further comprising an enclosed space for holding at         least one delivery.     -   69. The robot according to the preceding embodiment, further         comprising a secure access device for providing access to the         space.     -   70. The robot according to the preceding embodiment, wherein the         secure access device comprises a closure mechanism that is         controlled by a secure interface.     -   71. A combination of a robot according to any of the preceding         embodiments 37 to 70 and a delivery comprised within the robot,         wherein the center of mass of the combination is located between         the middle and the front end of the robot.     -   72. A mobile robot adapted to traverse vertical obstacles with a         predefined height, the robot comprising a frame structure having         a front end and a back end, the robot comprising         -   (a) at least one pair of front wheels positioned in             proximity of the front end of the structure, at least one             pair of back wheels positioned towards the back end of the             structure and at least one pair of middle wheels positioned             in between the front and back wheels;     -   and wherein the said wheels have radius r and are further         characterized by         -   (b) a maximum distance d between the at least one front             wheel and the at least one middle wheel measured from the             rear-most facing point of the at least one front wheel to             the front-most facing point of the at least one middle wheel             is defined by

$d = \frac{{6\; r^{2}} - {3\; {h \cdot r}}}{2\left( {h - r} \right)}$

where d is the said maximum distance, r is the radius of the wheel and h is the predefined height of the vertical obstacle.

-   -   73. A robot according to embodiment 72 wherein the frame         structure comprises an undercarriage that is structured so as to         be in vertical proximity of a line connecting the rear-most         facing point of the at least one front wheel to the front-most         facing point of the at least one middle wheel.     -   74. A robot according to any one of the embodiments 72 to 73         wherein the middle and back wheels are further characterized by         a maximum distance d′ between the at least one middle wheel and         the at least one back wheel measured from the rear-most facing         point of the at least one middle wheel to the front-most facing         point of the at least one back wheel defined by

$d^{\prime} = \frac{{6\; r^{2}} - {3\; {h^{\prime} \cdot r}}}{2\left( {h^{\prime} - r} \right)}$

where d′ is the said maximum distance, r is the radius of the wheel and h′ is the height of the vertical obstacle to be traversed.

-   -   75. A robot according to any one of the embodiments 72 to 74         wherein the frame structure comprises an undercarriage that is         structured so as to be in vertical proximity of the line         connecting the rear-most facing point of the at least one middle         wheel to the front-most facing point of the at least one back         wheel.     -   76. The robot according to any one of the embodiments 72 to 75,         adapted to traverse vertical obstacles of at least 18 cm height         with wheel radius of at least 10 cm and the maximum distance         between the front and middle wheels and/or the middle and back         wheels measured from the rear-most facing point of the front         wheel and/or middle wheel respectively to the front-most facing         point of the middle and/or back wheel of 4 cm.     -   77. A robot according to any one of the embodiments 72 to 76         further comprising at least two motors adapted to drive the         wheels.     -   78. A robot according to any one of the embodiments 72 to 77         further comprising at least one pushing device for exerting a         downward force with respect to the ground, selectively on the at         least one middle wheel.     -   79. A robot according to the preceding embodiment wherein the         pushing device is driven by a motor, preferably an electrical         motor.     -   80. A robot according to any of the preceding two embodiments,         wherein the pushing device is adapted such that when the robot         encounters a vertical obstacle along its direction of movement,         a downward and/or upward force can be applied by the device         through at least one pair of middle wheels, to facilitate the         traversal of the vehicle across the vertical obstacle.     -   81. A robot according to any of the preceding three embodiments,         wherein the pushing device is further adapted to exert a         downward and/or upward force through at least one pair of back         wheels.     -   82. A robot according to any of the preceding embodiments 78 to         81, wherein the robot further comprises a sensing device for         sensing obstacles along its forward direction of motion.     -   83. A robot according to the preceding embodiment, wherein the         sensing device is adapted to trigger the pushing device such         that a downward force is applied to at least the pair of middle         wheels of the robot to facilitate the movement of the front         wheels over the obstacles.     -   84. A robot according to any one of the preceding two         embodiments, wherein the sensing device comprises at least one         of: ultrasonic sensor, Lidar sensor, optical flow sensor, stereo         vision sensor, map-based localization device, bumping sensor,         odometry-based sensor and wheel slippage sensor.     -   85. A robot according to any one of the preceding three         embodiments, wherein the pushing device is further adapted to         communicate with the sensing device and apply a downward and/or         upward force on the middle wheels based on information from the         sensing device.     -   86. A robot according to any one of the embodiments 78 to 85,         wherein the pushing device comprises at least one tilting lever         connecting at least one middle and one back wheel, preferably         two shafts connecting middle and back wheels on each of the left         and the right sides of the robot.     -   87. The robot according to the previous embodiment, wherein the         pushing device is adapted to alternately apply force to the         middle wheels and the back wheels based on information from the         sensing device.     -   88. A robot according to the previous embodiment, wherein the         sensing device comprises means for communicating with a central         processing unit, and wherein the central processing unit         provides instructions to the pushing device based on information         received from the sensing device.     -   89. A robot according to any of the preceding three embodiments         wherein the tilting lever is adapted for at least angular motion         in the plane of the robot's wheels in order to apply a downward         and/or upward force with respect to the ground.     -   90. A robot according to any of the preceding embodiments 87 to         89, wherein the pushing device comprises a motor, and wherein         the first and second tilting levers are connected to a rear axle         at a first and second pivot point on the first and second axles,         respectively.     -   91. A robot according to the preceding embodiment, wherein the         pushing device is adapted for exerting angular force on first         and second shafts about the first and second pivot points, so as         to alternately generate a downward force on the middle wheels         and the back wheels.     -   92. A robot according to any of the preceding embodiments 78 to         91, wherein the pushing device is adapted to lift the middle         wheels, so that during climbing, their rotational center can         transiently extend vertically beyond that of the front wheels',         with respect to the vehicle frame.     -   93. A robot according to any of the preceding embodiments 78 to         92, wherein the pushing device is further adapted to lift and/or         push down the back wheels, so that when a downward force is         applied to the middle wheels, a counteracting upward force is         simultaneously applied to the back wheels, and when an upward         force is applied to the middle wheels, a counteracting downward         force is simultaneously applied to the back wheels.     -   94. A robot according to any of the preceding embodiments 77 to         93 wherein the motors driving the wheels and/or the pushing         device are electrical.     -   95. A robot according to any of the preceding embodiments 77 to         94, wherein the front wheels are driven.     -   96. A robot according to any of the preceding embodiments 77 to         95 comprising at least 4 (four) electric motors adapted to drive         the wheels.     -   97. A robot according to any of the preceding embodiments 72 to         96, wherein the robot's center of mass is located between the         middle and the front end of the robot.     -   98. A robot according to any of the preceding embodiments 72 to         97, wherein the robot's center of mass is located between the         middle of the robot and half of the distance from the middle to         the front end of the robot.     -   99. A robot according to any of the preceding embodiments 72 to         98, adapted for motion in an unstructured outdoor environment.     -   100. A robot according to any of the preceding embodiments 72 to         99, adapted to traverse vertical obstacles of a height of 10-30         cm, preferably 15-25 cm, more preferably about 20 cm.     -   101. A robot according to any one of the preceding embodiments         72 to 100, wherein the pairs of front, middle and back wheels         are connected on respective axles.     -   102. The robot according to the previous embodiment, wherein the         distance between wheels on each of the axles is approximately         equal.     -   103. A robot according to any of the preceding embodiments 72 to         102, wherein the wheel diameter is 10-30 cm, preferably 15-25         cm, more preferably about 20 cm.     -   104. A robot according to any of the preceding embodiments 72 to         103, wherein the wheels protrude beneath the frame by at least 5         cm, preferably at least 6 cm, more preferably by at least 7 cm.     -   105. A robot according to any of the preceding embodiments 72 to         104, wherein the front wheels protrude in front of the frame         structure by 1 to 8 cm, preferably by 1 to 6 cm, more preferably         by 2 to 5 cm.     -   106. A robot according to any of the preceding embodiments 72 to         105, wherein the wheels comprise pneumatic tires made of a         caoutchouc compound.     -   107. A robot according to any of the preceding embodiments 72 to         106, wherein the static friction coefficient μ_(s) between the         wheels and the obstacle is 0.9-1.1 for dry surface and 0.2-0.4         for wet surface.     -   108. The robot according to any one of the preceding embodiments         72 to 107, further comprising a space for holding at least one         delivery.     -   109. The robot according to any one of the preceding embodiments         72 to 108, further comprising an enclosed space for holding at         least one delivery.     -   110. The robot according to the preceding embodiment, further         comprising a secure access device for providing access to the         space.     -   111. The robot according to the preceding embodiment, wherein         the secure access device comprises a closure mechanism that is         controlled by a secure interface.     -   112. A combination of a robot according to any of the preceding         embodiments 72 to 111 and a delivery comprised within the robot,         wherein the center of mass of the combination is located between         the middle and the front end of the robot.     -   113. A climbing method comprising         -   (a) approaching a vertical obstacle with a mobile robot             comprising a frame structure having a front end and a back             end, the robot comprising at least one front wheel             positioned in proximity of the front end of the structure,             at least one back wheel positioned in proximity of the back             end of the structure, and at least one middle wheel             positioned in between the front and back wheels, and at             least one further wheel either in a front, middle and/or             back position; wherein the at least one front wheel, the at             least one back wheel and the at least one middle wheel are             arranged on the frame structure such that the robot is             supported by said wheels during normal travel along a             surface; the robot further comprising at least two motors             adapted to drive the wheels, and a motor-driven device for             exerting a downward force with respect to the ground,             selectively on at least the at least one middle wheel;         -   (b) sensing the vertical obstacle with one or more sensing             devices disposed on the robot;         -   (c) actuating the one or more front wheels with one or more             motors to permit the one or more front wheels to start             climbing the vertical obstacle;         -   (d) actuating the one or more middle and/or back wheels with             one or more motors to provide a forward momentum of the             robot and thereby increase friction between the one or more             front wheels and the vertical obstacle;         -   (e) exerting a downward force on the one or more middle             wheels with the motor-driven device so as to provide a             counteracting vertical force on the one or more front wheels             and increase traction of the middle wheels, thereby             facilitating the climbing of the front wheels;         -   (f) ceasing applying the downward force on the one or more             middle wheels after the front wheels have reached the top of             the obstacle; and         -   (g) completing climbing of the obstacle through the forward             momentum of the robot generated by actuating the middle             and/or back wheels.     -   114. The method of embodiment 113, wherein the actuation of         front, middle and/or back wheels is performed simultaneously.     -   115. The method of embodiment 113, wherein the front, middle and         back wheels are all actuated as the robot approaches the         vertical obstacle.     -   116. The method of any one of the embodiments 113 to 115 wherein         the method further includes sensing the position of the front         wheels on the obstacle by means of the at least one sensing         device before ceasing applying the downward force on the one or         more middle wheels.     -   117. The method of any one of the embodiments 113 to 116,         wherein the motor-driven device comprises a mechanism for         providing alternating downward and upward force on the middle         wheels and back wheels, and wherein the method further comprises         in step (e) exerting an upward force on the back wheels         simultaneously to the exerting a downward force on the middle         wheels, by means of the motor-driven device, and wherein the         method further comprises, following step (f):         -   (g) reversing the application of force on the middle and             back wheels, so that a downward force is applied to the back             wheels and an upward force on the middle wheels, to             facilitate the climbing of the middle wheels of the             obstacle, and         -   (h) completing climbing of the obstacle through the forward             momentum of the robot generated by actuating the middle             and/or back wheels.     -   118. The method of embodiment 117, further comprising ceasing         applying downward or upward force on the middle or back wheels         after the sensing device determines that the back wheels have         reached the top of the obstacle.     -   119. The method of any one of the embodiments 113 to 118,         wherein the mobile robot is a robot or combination as described         in any one of the embodiments 1 to 112.     -   120. A mobile robot, particularly according to any one of the         preceding embodiments 1 to 112, comprising         -   (a) a frame with at least one front wheel, at least two             middle wheels and at least two rear wheels;         -   (b) wherein at least one middle wheel and at least one rear             wheel are connected by a tilting lever that is arranged on             each of opposing sides of or to the frame; and         -   (c) wherein each tilting lever can be turned around a lever             bearing located between the respective axial centers of             rotation of each pair of wheels.     -   121. A robot according to embodiment 120 wherein the tilting         lever is adapted to rotate freely until a certain angle is         reached, particularly when the robot encounters uneven ground         along its direction of movement, allowing the robot to traverse         such uneven ground smoothly.     -   122. A robot according to any of the preceding embodiments 120         or 121 wherein the tilting lever can be turned around the lever         bearing by at most 60°, preferably on either side.     -   123. A robot according to any of the preceding embodiments 120         to 122 wherein the tilting lever can be turned around the lever         bearing by at most 55°, preferably on either side.     -   124. A robot according to any one of embodiments 120 to 123         wherein the tilting lever can be turned around the lever bearing         by at most 50°, preferably on either side.     -   125. A robot according to any one of embodiments 120 to 124         wherein the tilting lever can be turned around the lever bearing         by at most 45°, preferably on either side.     -   126. A robot according to any one of embodiments 120 to 125         wherein the tilting lever can be turned around the lever bearing         by at most 40°, preferably on either side.     -   127. A robot according any one of embodiments 120 to 126 wherein         the tilting lever can be turned around the lever bearing by at         most 35°, preferably on either side.     -   128. A robot according to any one of embodiments 120 to 127         wherein the tilting lever can be turned around the lever bearing         by at most 30°, preferably on either side.     -   129. A robot according to any one of embodiments 120 to 128         wherein the tilting lever can be turned around the lever bearing         by at most 25°, preferably on either side.     -   130. A robot according to any one of embodiments 120 to 129         wherein the tilting lever can be turned around the lever bearing         by at most 20°, preferably on either side.     -   131. A robot according to any one of embodiments 120 to 130         further comprising a sensor adapted to sense the absolute and/or         relative angular position of the tilting lever.     -   132. A robot according to embodiment 131 wherein the sensor is         adapted to sense the absolute and/or relative angular position         of the tilting lever is at least one Hall effect non-contact         rotary position sensor.     -   133. A robot according to embodiment 133 wherein the sensor         adapted to sense the absolute and/or relative angular position         of the tilting lever is any one or a combination of at least one         potentiometer, at least one optical encoder, at least one         magnetic encoder and/or at least one visual camera-like system.     -   134. A robot according to any one of embodiments 131, 132 or 133         wherein the sensor is adapted to sense the relative angular         position of the tilting lever is calibrated at the beginning of         operation, preferably by moving the lever to an extreme position         and by calibrating it there.     -   135. A robot according to any one of embodiments 131 to 134,         further comprising a lever turn motor and wherein the lever turn         motor is adapted to start actuating the tilting lever upon         receiving sensor data.     -   136. A robot according the preceding embodiment wherein the         sensor data can comprise tilting angle, force applied to any of         the wheels, visual data, Lidar data and or Hall effect         non-contact rotation sensor data.     -   137. A robot according to any of the embodiments 120 to 136         wherein the tilting lever can rotate freely and/or be actuated         by a lever turn motor.     -   138. A robot according to any one of the embodiments 120 to 137         wherein the tilting levers on each side can be rotate freely         and/or actuated by a lever turn motor independent from each         other.     -   139. A robot according to any one of the embodiments 120 to 138         wherein the tilting levers on each side can rotate freely with         the lever turn motor connected to the tilting levers slightly         resisting the rotation.     -   140. A robot according to any one of the embodiments 120 to 139         wherein the tilting levers on each side can be rotated freely,         the robot further comprising a clutch that can disconnect the         lever turn motor driving the tilting levers.     -   141. A robot according to any of the embodiments 120 to 140         wherein the robot is adapted to climb obstacles of up to 18 cm         by rotating the tilting lever.     -   142. A robot according to any of the embodiments 120 to 141         wherein the tilting lever is adapted to rotate freely until a         particular inclination angle is reached, at which point the         tilting turn motor is adapted to engage, such point being the         engagement point.     -   143. A robot according to the preceding embodiment wherein the         tilting turn motor is adapted to engage after the tilting lever         has rotated freely for at least 10°, more preferably such as at         least 15°, more preferably such as at least 20° and even more         preferably such as at least 25°.     -   144. A robot according to any of the preceding two embodiments         wherein the tilting lever is adapted to rotate freely over a         range of 25° -45° from one engagement point to the next.     -   145. A climbing method of a mobile robot comprising one front         wheel, at least two middle wheels and at least two rear wheels,         wherein the robot can be as described in claims 1-16, said         method consisting of         -   (a) providing a mobile robot comprising a frame with at             least one front wheel, at least two middle wheels and at             least two rear wheels; and         -   (b) connecting the at least one middle wheel and the at             least one rear wheel by a tilting lever that is arranged on             each of the opposing sides of or to the frame, forming a             pair of wheels; and         -   (c) turning the tilting lever around a lever bearing located             between the respective axial centers of rotation of each             pair of wheels when traversing an obstacle.     -   146. A climbing method according to the embodiment 145 further         comprising the steps of         -   (d) engaging at least one lever turn motor once the tilting             lever reaches a certain tilting angle; and         -   (e) exerting a downward force on the middle wheels with a             mechanism driven by the at least one lever turn motor so as             to provide a counteracting vertical force on the one or more             front wheels and increase traction of the middle wheels,             thereby facilitating the climbing of the front wheels; and         -   (f) ceasing exerting the downward force on the one or more             middle wheels after the front wheels have reached the top of             the obstacle; and         -   (g) completing climbing of the obstacle through the forward             momentum of the robot generated by actuating the middle             and/or back wheels.     -   147. The method according to any of the preceding two         embodiments, wherein the front, middle and back wheels are all         actuated as the robot approaches the vertical obstacle.     -   148. The method according to any of the preceding three         embodiments, wherein the method further includes sensing the         position of the front wheels on the obstacle by means of the at         least one sensing device before ceasing applying the downward         force on the one or more middle wheels.

As will be apparent to the skilled person, the method can be realized using any robot as described in the foregoing description and the following description of embodiments. In particular, the method can be realized with various configurations of wheel configuration, and mechanisms for actively applying force to the middle and/or back wheels, as described herein.

The above features along with additional details of the invention, are described further in the examples below, which are intended to further illustrate the invention but are not intended to limit its scope in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view onto a robot embodiment in accordance with the present invention;

FIG. 2 shows a schematic and exemplifying arrangement of elements in accordance with the present invention.

FIG. 3 shows an embodiment in accordance with the present invention before, during and after the traversal of a curbstone.

FIG. 4a shows just the wheels of the robot according to one embodiment is with wheels aligned; and

FIG. 4b shows the embodiment according to FIG. 4a indicating the movement of the tilting lever and the attached rear wheels.

FIG. 5a shows a schematic embodiment of elements of the tilting lever in accordance with the present invention

FIG. 5b shows an inclined embodiment according to FIG. 5 a.

FIG. 5c shows an embodiment of elements of the tilting lever and lever turn motor according to the invention.

DESCRIPTION OF VARIOUS EMBODIMENTS

In the following, exemplary embodiments of the invention will be described, referring to the figures. These examples are provided to provide further understanding of the invention, without limiting its scope.

In the following description, a series of features and/or steps are described. The skilled person will appreciate that unless required by the context, the order of features and steps is not critical for the resulting configuration and its effect. Further, it will be apparent to the skilled person that irrespective of the order of features and steps, the presence or absence of time delay between steps, can be present between some or all of the described steps.

As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

Throughout the description and claims, the terms “comprise”, “including”, “having”, and “contain” and their variations should be understood as meaning “including but not limited to”, and are not intended to exclude other components.

The present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., “about 3” shall also cover exactly 3 or “substantially constant” shall also cover exactly constant).

The term “at least one” should be understood as meaning “one or more”, and therefore includes both embodiments that include one or multiple components.

Furthermore, dependent claims that refer to independent claims that describe features with “at least one” have the same meaning, both when the feature is referred to as “the” and “the at least one”.

It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Alternative features serving the same, equivalent or similar purpose can replace features disclosed in the specification, unless stated otherwise. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

Use of exemplary language, such as “for instance”, “such as”, “for example” and the like, is merely intended to better illustrate the invention and does not indicate a limitation on the scope of the invention unless so claimed. Any steps described in the specification may be performed in any order or simultaneously, unless the context clearly indicates otherwise.

All of the features and/or steps disclosed in the specification can be combined in any combination, except for combinations where at least some of the features and/or steps are mutually exclusive. In particular, preferred features of the invention are applicable to all aspects of the invention and may be used in any combination.

Reference numerals have just been referred to for reasons of quicker understanding and are not intended to limit the scope of the present invention in any manner

FIG. 1 shows one example of a robot 1 in accordance with the invention.

As can be seen the robot can comprise a body 2 and a lid 3. Other configurations for different applications are also possible. The robot embodiment shown can be particularly used for the transfer of deliveries (such as mail, groceries, parcels, packages, flowers and/or purchases). For communication reasons further electronics, telecommunication devices, computers, sensors etc. or parts thereof can be used. In the embodiment shown an antenna 4 is also shown.

A undercarriage or frame 5 is particularly arranged at the bottom of the robot 1. As can be seen in the embodiment shown 3 sets or pairs of wheels are provided, one or more front wheels 10, one or more middle wheels 20 and one or more rear wheels 30. The front wheels 10 can be steered and can slightly protrude in front of the body 2. Also other wheels may be steered. The wheels 10, 20, 30 could also be covered by any kind of shields and/or can be integrated into the body 2.

FIG. 2 shows a schematic sketch only. Reference numerals are provided for elements on one side only, in case further corresponding elements are provided on the other side. The front wheels 10 can be driven and can extend over the front part of the body 2 and/or frame 5 for the reasons described before. A front motor 12 can drive a front axle 11 and the front wheel 10 being attached. As mentioned before, the front wheels 10 can be steered which is not shown. A front control 14 can control the front motor 12 and can also be connected to a central or intermediate robot control (not shown). The front wiring 13 can connect the front control 14 and the front motor 12. The same applies to the other side, i.e. to the other front wheel, front motor and front control (not numbered). A central motor driving both front wheels 10 can also be provided, but requires more elements. The arrangement shown can thus be an easier, more reliable and less expensive design.

The middle wheels 20 can be connected by a common middle axle 21 but could also be driven by individual axles (not shown).

The rear wheels 30 can be connected by a common rear axle 31 but could also be driven by individual axles (not shown).

Besides the options mentioned already, an embodiment particularly for moving the middle wheels 20 away from the body and/or frame 5 is shown for tilting the arrangement of middle wheels 20 and rear wheels 30. A tilting assembly 40 can do this. In the embodiment shown, the middle wheels 20 and the rear wheels 30 are driven together by rear motors 44. Alternatively, a common motor (not shown) could be arranged for driving all wheels in the middle and in the rear. The motors 44 are driving a lever shaft 43 and the rotational movement and/or force will be further delivered to the middle wheels 20 and rear wheels 30 by a mechanism not shown. This mechanism could be any known means for transferring and/or gearing the rotational movement, such as by gear(s), pulley(s), chain(s) etc. or any combination thereof. Alternatively, the motors could also be located in the wheels or on the axles the wheels are directly connected to. This can apply to all wheels. A respective rear control 46 can control the rear motor 44 either individually on each side or one rear control 46 could also control the rear motors 44 together. The rear control 46 can also communicate with a central control (not shown).

A tilting lever or tilting shaft 41 or a unit working as a connection between the middle wheels 20 and the rear wheels 30 fixes these wheels in relation to each other. The tilting lever 41 can be turned and will allow the wheels 20, 30 to be driven and to tilt.

A tilting axle (lever bearing) 42 allows the arrangement of the middle wheels 20 and rear wheels 30 as well as the tilting lever 41 to turn. The tilting axle (lever bearing) 42 can be turned itself by a turning mechanism 47 for transferring and/or gearing a rotational movement, such as by gear(s), pulley(s), chain(s) etc. or is any combination thereof. The rotational movement is provided, when needed, by a turning motor 49 driving a turning shaft 48 which will then make the tilting axle (lever bearing) 42 turn over the turning mechanism 47. A turning control 51 is connected with the turning motor 49 by a turning wiring 50. Again, the turning control 51 and turning wiring 50 may also communicate with a more central control (not shown).

The tilting assembly 40 can just be arranged on one side but also on both sides. In case it is arranged on one side, the middle wheels 20 and the rear wheels 30 can be connected by the axes 21 and 31, respectively.

FIG. 3 shall exemplify different situations of climbing an obstacle, such as a curbstone, by the robot 1. For reasons of clarity, reference numbers are just shown in sketch no. 1. Middle wheels 20 and rear wheels 30 are both connected to a tilting lever 41. A curbstone 60 is shown being approached by the robot 1. In case of no other sensors, the front wheels 10 may touch the curbstone. This can initiate the climbing of the robot 1 onto the curbstone, as shown in sketch no. 2. The traction of the front wheel onto the curbstone's vertical surface, the movement of the middle wheels away from the robot generated by rotational movement of the tilting lever 41, the movement of the rear wheels towards the body of the robot and/or the forward momentum of the robot, aided by the force applied by the driven middle and/or rear wheels to keep the front wheels in contact with the curbstone vertical surface initiate the climbing of the robot as shown. A motor for driving the tilting lever (not shown) will be turned on at this stage, so as to apply rotational force to the tilting lever 41.

When the front wheels are on top of the curbstone, as shown in sketch no. 3, the middle wheels are further moved towards the curbstone by the moving robot 1 until they touch the curbstone 60 as shown in sketch no. 4. During this phase, the tilting of the robot is at its maximum, at least for the curbstone shown. A further tilting may be possible when climbing a higher curbstone.

In sketch no. 5, the middle wheels are climbing up the curbstone and the tilting action of the tilting mechanism is reversed, such that the middle wheels move towards the frame of the robot, while the back wheels move away from the robot, driven by the tilting lever 41. It will even reverse further as is apparent from sketch no. 6. By this action, maximum traction of all wheels and maximum stability of the robot during climbing can be obtained.

During further progress of the robot, the tilting assembly will return back to a neutral position so that the wheels are in one plane or generally in one plane again. This is demonstrated in sketch no. 8. During such forward motion, the tilting mechanism is in a neutral position, and the motor driving the tilting mechanism is generally switched off.

It is not necessary to keep all wheels on the ground at all times, and this may even not be feasible when the robot reaches an obstacle under another angle than shown in FIG. 3. However, the robot can be designed and programmed to approach obstacles perpendicularly so that a stable and successful climbing of obstacles can be achieved.

FIG. 4 shows a side view of one embodiment of the wheels of the robot wherein two back wheels are arranged on a tilting lever 41 that sits on a lever shaft (not shown). In FIG. 4a , the wheels 10, 20, 30 are all horizontally or essentially horizontally aligned (with respect to ground) on a straight line and the tilting lever 41 is aligned to or parallel to the frame of the robot (not shown). The tilting lever 41 is adapted to rotate around the lever bearing 42 so that the middle wheel 20 and the back wheel 30 move ascend or descend, depending on the direction of rotation. Thus, during clockwise rotation the back wheel 30 descends and the center wheel ascends, while the during anticlockwise rotation the movement of the center and back wheels is reversed.

Thus, as shown in FIG. 4b , the tilting lever 41 can rotate by any given value of the angle β, where β=0 when the wheels are horizontally aligned. The tilting lever 41 can for example be adapted to rotate up to 60° in either direction around the lever bearing 42, resulting in an overall rotation of up to 120°. In a preferred embodiment, the tilting lever 41 can rotate up to 55° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 50° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 45° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 40° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 35° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 30° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 25° in either direction. In another preferred embodiment, the tilting lever 41 can rotate up to 20° in either direction.

FIG. 5a shows a schematic embodiment of the inside structure of the tilting lever 41. The tilting gear frame 411 can comprise different shapes as long as it provides adequate support and flexural strength to function as intended. The tilting gear frame 411 can be made from a metal and/or a metal alloy. The tilting gear 412 can be made of the same material as the tilting gear frame 411 and can comprise a part of it. The tilting gear teeth 413 can comprise a part of the tilting gear 412 and can also be made of the same material. In this way, the tilting gear frame 411, the tilting gear 412 and the tilting gear teeth 412 can all comprise one solid part of the tilting lever 41. Note that in the present embodiment, four tilting gear teeth 413 are shown, but there can be as well two tilting gear teeth covering a wider radius. The tilting axle 42 can be seen protruding from the center of the tilting gear 412. It can be fixed in this position by a mechanism not shown, or simply by the tilting gear teeth 413. The tilting axle 42 comprises tilting axle teeth 421 also fixed within the tilting gear 412. The tilting gear frame 411 is adapted to rotate around the tilting axle 42 along with the tilting axle teeth 421. The tilting gear teeth 413 can rotate freely along with the tilting gear frame 411 until they reach the tilting axle teeth 421. This is further shown in FIG. 5 b.

FIG. 5b demonstrates the same schematic embodiment of the inside structure of the tilting lever 41 as FIG. 5a rotated by an angle β. After such rotation, the tilting gear teeth 413 and the tilting axle teeth 421 are aligned and in contact. Any further rotation in the same direction can not be performed freely and would require actuating by the lever turn motor 49 (not shown here). A skilled person will understand that the angle β can be variable and can depend on the desired application.

For the mobile robot as described herein, this arrangement is beneficial, since smaller obstacles can be climbed without engaging the lever turn motor 49. In such a way, the robot can traverse irregularities on the sidewalk of a height such as 5 cm without engaging the lever turn motor 49. When traversing higher obstacles, such as curbstones of 15 cm or so, the robot can tilt the tilting lever freely 41 until the angle β and then proceed with climbing by engaging the lever turn motor 49. The tilting lever 41 can for example be adapted to rotate freely for about 25°-45° from one engagement point all the way to the next, i.e. for about 12.5°-22.5° from a horizontal position to a maximally inclined position before engaging the motor. In a preferred embodiment, the robot can be adapted to engage the lever turn motor 49 past this point. A skilled person will also understand that the inclined embodiment shown in FIG. 5b can roughly correspond to the inclined embodiment shown in FIG. 4 b.

FIG. 5c demonstrates a side view of the schematic embodiment of the inside structure of the tilting lever 41 along with some further parts of the tilting mechanism. The tilting gear frame 411 is shown sideways along with the tilting gear 412. In this embodiment, the tilting axle 42 can be seen slightly protruding outward from the tilting gear 412. The lever turn mechanism 47 is shown schematically here and can comprise further gears, and/or pulleys. The lever turn shaft 48 connects to the lever turn motor 49 that is adapted to drive the tilting lever 41.

LIST OF REFERENCE NUMERALS

-   1—robot -   2—body -   3—lid -   4—antenna -   5—frame/carriage -   10—front wheel -   11—front axle -   12—front motor -   13—front wiring -   14—front control -   20—middle wheel -   21—middle axle -   30—rear wheel -   31—rear axle -   40—tilting assembly -   41—tilting lever (tilting shaft) -   42—lever bearing -   43—lever shaft -   44—rear motor -   45—rear wiring -   46—rear control -   47—lever turn mechanism -   48—lever turn shaft -   49—lever turn motor -   50—lever turn wiring -   51—lever turn control 

We claim:
 1. A mobile robot adapted to traverse at least vertical obstacles, the robot comprising a frame structure having a front end and a back end, and further having a front section, a middle section and a back section, the robot further comprising: (a) at least one front wheel positioned in the front section of the robot and extending beyond it in the front, at least one back wheel positioned in the back section of the robot, and at least one middle wheel positioned in the middle section of the robot; (b) at least one further wheel positioned either in the front section, middle section and/or back section of the structure; (c) a motor-driven device for exerting a downward and/or upward force with respect to the ground, selectively on the at least one middle wheel; and (d) at least two motors, each of which being adapted to drive the wheels and/or the motor-driven device.
 2. The robot of claim 1, wherein the robot comprises at least one pair of front wheels positioned in proximity of the front end of the structure, at least one pair of back wheels positioned towards the back end of the structure and at least one pair of middle wheels positioned in between the front and back wheels.
 3. The robot of claim 1, wherein the pairs of front, middle and back wheels are connected on respective axles.
 4. The robot of claim 2, wherein the distance between the wheels on each of the axles is approximately equal.
 5. The robot of claim 1, wherein the motor-driven device is adapted such that when the robot encounters a vertical obstacle along its direction of movement, a downward and/or upward force can be applied by the motor-driven device through the at least one middle wheel, to facilitate the traversal of the vehicle across the vertical obstacle.
 6. The robot of claim 1, wherein the motor-driven device is further adapted to exert a downward and/or upward force through the at least one back wheel.
 7. The robot of claim 1, wherein the robot further comprises a sensing device for sensing obstacles along its forward direction of motion, said sensing device comprising at least one or a combination of: an ultrasonic sensor, a Lidar sensor, an optical flow sensor, a stereo vision sensor, a map-based localization device, a bumping sensor, an odometry-based sensor and/or a wheel slippage sensor.
 8. The robot of claim 7, wherein the sensing device is adapted to trigger the motor-driven device such that a downward force is applied to at least the middle wheels of the robot to facilitate the movement of the front wheels across the obstacles.
 9. The robot of claim 7, wherein the motor-driven device is further adapted to communicate with the sensing device and apply a downward force and/or upward force on at least the middle wheels and/or on at the back wheels based on information from the sensing device.
 10. The robot of claim 1, wherein the front wheels are driven.
 11. The robot of claim 1, wherein all of the wheels are driven.
 12. The robot of claim 11, comprising two motors for driving each of two front wheels and two motors for driving two sets of middle and back wheels, each of said motors driving at least one middle wheel and a back wheel that is disposed along one side of the robot.
 13. The robot of claim 1, wherein the robot's center of mass is located between the middle and the front end of the robot, preferably between the middle of the robot and half of the distance from the middle to the front end of the robot.
 14. The robot of claim 1 adapted for motion in an unstructured outdoor environment.
 15. The robot of claim 1 adapted to traverse vertical obstacles of a height of about 10 to about 25 cm, such as about 15 to about 20 cm, such as curbstones.
 16. The robot of claim 1, wherein the wheel diameter is 10-30 cm, preferably 15-25 cm, more preferably about 20 cm.
 17. The robot of claim 1, wherein the front wheels protrude in front of the frame structure by 1 to 8 cm, preferably by 1 to 6 cm, more preferably by 2 to 5 cm.
 18. The robot of claim 1, wherein the wheels protrude beneath the frame by at least 5 cm, preferably at least 6 cm, more preferably by at least 7 cm.
 19. The robot of claim 1, wherein the front wheel(s), the back wheel(s) and the center wheel(s) are arranged on the frame structure such that the robot is supported by at least two wheels during normal travel along a surface.
 20. The robot of claim 1, further comprising an enclosed space for holding at least one delivery.
 21. The robot of claim 1, wherein the wheels have the same radius and wherein the maximum distance d between the at least one front wheel and the at least one middle wheel or between the at least one middle wheel and the at least one back wheel measured from the rear-most facing point of the at least one middle wheel is defined by ${d = \frac{{6\; r^{2}} - {3\; {h \cdot r}}}{2\left( {h - r} \right)}},$ where d is the said maximum distance, r is the radius of the wheels and h is the maximum traversable height of the obstacle.
 22. A combination of a robot according to claim 1 and a delivery comprised within the robot, wherein the center of mass of the combination is located between the middle and the front end of the robot.
 23. A climbing method of a mobile robot, said method comprising: (a) approaching a vertical obstacle with said mobile robot, said robot comprising: (i) a frame structure having a front end and a back end, (ii) at least one front wheel positioned in proximity of the front end of the structure, (iii) at least one back wheel positioned in proximity of the back end of the structure, (iv) at least one middle wheel positioned in between the front and back wheels, and (v) at least one further wheel either in a front, middle and/or back position; wherein the at least one front wheel, the at least one back wheel and the at least one middle wheel are arranged on the frame structure such that the robot is supported by said wheels during normal travel along a surface; the robot further comprising (vi) at least two motors adapted to drive the wheels, and (vii) a motor-driven device for exerting a downward force with respect to the ground, selectively on at least the at least one middle wheel; (b) sensing the vertical obstacle with one or more sensing devices disposed on the robot; (c) actuating the one or more front wheels with one or more motors to permit the one or more front wheels to start climbing the vertical obstacle; (d) actuating the one or more middle and/or back wheels with one or more motors to provide a forward momentum of the robot and thereby increase friction between the one or more front wheels and the vertical obstacle; (e) exerting a downward force on the one or more middle wheels with the motor-driven device so as to provide a counteracting vertical force on the one or more front wheels and increase traction of the middle wheels, thereby facilitating the climbing of the front wheels; (f) ceasing applying the downward force on the one or more middle wheels after the front wheels have reached the top of the obstacle; and (g) completing climbing of the obstacle through the forward momentum of the robot generated by actuating the middle and/or back wheels.
 24. The method of claim 23, wherein the method further includes sensing the position of the front wheels on the obstacle using the at least one sensing device before ceasing applying the downward force on the one or more middle wheels.
 25. The method of claim 23, wherein the motor-driven device comprises a mechanism for providing alternating downward and upward force on the middle wheels and back wheels, and wherein the method further comprises, in (e), exerting an upward force on the back wheels simultaneously to the exerting a downward force on the middle wheels, using the motor-driven device, and wherein the method further comprises, following (f): (g1) reversing the application of force on the middle and back wheels, so that a downward force is applied to the back wheels and an upward force on the middle wheels, to facilitate the climbing of the middle wheels of the obstacle.
 26. The method according to claim 25, further comprising ceasing applying downward or upward force on the middle or back wheels after the sensing device determines that the back wheels have reached the top of the obstacle. 